Sapogenin derivatives and preparation of same



Patented Feb. 19, 1946 SAPOGENIN DERIVATIVES AND PREPARATION OF Russell Earl Marker, Mexico City, Mexico, and

Harry Means Crooks, Jr., and Eugene Leroy Wittle, Detroit, Mich., assignors to Parke, Davis & Company, Detroit, Mich., a corporation of Michigan No Drawing. Original application May 15, 1941, Serial No. 393,666. Divided and this application May 24, 1944, Serial No. 537,198

4 Claims.

The invention relates to the preparation of steroidal compounds and this application is a division of our copending application, Serial No. 393,666, filed May 15, 1941, now Patent No. 2,352,- 851, issued July 4, 1944.

This application relates more particularly to the preparation of glycosidic derivatives of 20-keto- 16- (a-acyloxy-isocaprooxy) -pregnane compounds and the hydrolysis of the same by alkaline agents to obtain A -20-keto-pregnene compounds having unacylated sugar residues attached to the steroid nucleus.

According to this invention, the pseudo-sapogenins .or their ring A and/or B glycosidic derivatives are prepared by reacting glycosidie derivatives of the sapogenins with acidic agents, for example, acylating agents such as acid anhydrides, under conditions more vigorous than those required merely for acylation.

By glycosidic derivatives of the sapogenins we mean sapogenin derivatives in which sugar residues are attached through a hemi-aceta1 linkage to the cyclopentanoperhydrophenanthrene nucleus. In general, the exact nature of the structures of these substances are not known with certainty. The following formulae illustrate various types of the above sapogenin glycosides:

HOH (5110B (EHOH 27H (BEE- lHz 3111011 IX. Trillarln Gila-CH:

(EH-CH A, OCa

( JHOH CHOH CEOH (3H JHIOH CH: H

- Generally speaking the glycosides of the steroidal sapogenins may be classified as (1) sapsimpler glycosides difier from the saponins in that (1) they contain fewer, i. e., one to three, sugar units; (2) they are more readily obtained crystalline; (3) they do not show marked capillary active properties. In most cases, including the compounds represented by VIII, IX, and X, the exact nature of the glycosidic linkages is not definitely known; that is, it is not known whether the sugars have a furanose or pyranose structure, nor which carbon atoms of the different sugar units are (through oxygen) united. In many cases even the number and kind of sugar units present are not known.

See further, Fieser, Chemistry 'of Natural Products Related to Phenanthrene, 2nd ed., p. 333 ff. (Reinhold Publishing Corporation, New York city,1937).

Since the steroidal sapogenins occur in nature, not in the free form, but combined with sugar units as glycosidic derivatives, the present invention makes it unnecessary to. isolate the sapog-' enins. Instead, their more readily available g1y cosides may be converted directly to pseudosapogenin derivatives. This elimination of a formerly essential step results in higher yields of steroidal hormones from plant sources.

As naturally occurrin glycosidic derivatives of steroidal sapogenins which may be used in the practice of this invention, there may be mentioned amolonin, sarsasaponin, digitonin, or like steroidal saponins. Also, there may be used partially degraded glycosidic derivatives of these saponins, such as trillarin or trillin. Such partially degraded glycosidic derivatives of saponins are obtained by hydrolyzing the saponin at some of the oligosaccharide linkages by means of enzymes or dilute acids or similar reagents. Again, there may be used synthetic glycosiolic derivatives of steroidal sapogenins such as the synthetic galactosides, glucosides, ribosides, and other giycosides of sapogenins such as sarsasapogenin, diosgenin, or other steroidal sapogenins containing reactive nuclear hydroxyl groups. Synthetic glycoside suitable for the practice of this invenv tion may also be prepared from sapogenins which have reactive nuclear hydroxyl groups, but which are not aglycones of naturally occurring saponins. tion may also be prepared from sapogenins which For example, although neither epi-sarsasapogenins nor its-glycosides occur in nature, glycosides of epi sarsasapogenin may be prepared synthetically from sarsasaponin by converting the latter into its aglycone, sarsasapogenin, and then con- 7 verting this into epi-sarsasapogenin. The episarsasapogenin may then be treated to form the glycoside as for example by treatment with bromoacetoglucose.

The conversion of the glycosidic derivativ of the steroidal sapogenin into an acylated glycosidic 3 pseudo-sapogenin may be effected by treating the former with an ,acylating agent under conditions more vigorous than those required for. mere acylation. This step may be effected, I Qr--X- ample, by treatment of the glycosidic deriyatiyes" of the sapogenins with a carboxylic anhydride at PIS-250 C. We have found that best results are obtained with lower fatty acid anhydrides while maintaining the reaction temperature in formed is an acylated glycosidic pseudo sapogenin derivative acylated at least at the exo hydroxyl attached to ring D with'production of an acylated the neighborhood of 200 The product tlius' alkaline reagents.

glycosidic derivative of a steroid having in ring D the structure In this case the remainder of the steroid molecule containing the acylated sugar residues remain substantially unaiiected during the oxidationand the product may then be hydrolyzed with production of a steroid having in ring D the structure D H V a The above hydrolysis acts both upon the 6- acyloXy-isocaproox-y group attached to 0-16 and the acylated sugar residues in the other portions of the steroid nucleus. down with regard to the products formed during this hydrolysis. The t-acyloxy-isocaprooxy group at (7-16 is hydrolytically removed with production of a steroid having in ring D the structure CH: I U

under conditions of very mild hydrolysis, as for example by treatment with dilute acidic or For instance, this groupis removed by warming the steroid with dilute a1- coholic hydrochloric acid, dilute sodium carbonate solution or dilute barium hydroxide solution. On the other hand, the acylated'sugar residues in the remainder of the molecule are affected different1y, depending on whether the conditions .of

hydrolysis are alkaline or acidic. Mild alkaline hydrolysis removes only the acyl groups attached to the sugar residue, while leaving' the su r residues still attached to the steroid nucleus. However, acid hydrolysis removes the sugar residues as well, thereby leaving hydroxyl groups in the steroid nucleus at the position to which the sugar residues were formerly attached; Suitable alkaline reagents for removal of the acyl groups from the sugar residues, whil leaving the unacylated sugar residues thus formed still'fattached to the steroid nucleus, include cold sodium methylate solution, barium hydroxide solution, calcium hydroxide solution and col'dfsodiuni hydroxide solution. The acidic hydrolysis required to remove the sug ar residues from the steroid nucleus is best achieved by boiling thesubstance with alcoholic hydrochloric acid; However, other acidic reagents sucha-s dilute sulfuric acid, or other mineral acids may be usedinstead-u The step of oxidation referredto in" the above description is best accomplished underrelatively mild conditions? We have found that best-results are obtained if-the pseudo-'sapogenin derivatives are oxidized below 50 C. bymeans .of a n-oxidizing agent of the class consisting of chromic and permanganic acids and their salts. "However, other oxidizing agents such as ozone, hydrogen peroxide, and the 'likemay. effectively be employed in thisstep. Particularly satisfactor results are obtained When'the' oxidation is conduted at Certain rulescan be set -35 G. in acetic acid; using chromic anhydride as the oxidant. i

Our invention may be further illustrated by the following examples.

Example 1 The saponinfrom Trillium erectum is obtained and converted into the acetate of Trillium erectum pseudo-saponin as described in Serial No.[3'93,666.f This product is dissolved in Z liters of glacial, acetic acid and, added at 30 C. toa stirred solution of g. of chromic anhydride in 1 liter of 60% acetic acid After the mixture has stood one and a'half hours at this temperature,

the excess chromic anhydrideis destroyed by addition of zinc powder. The solution is filtered from excess zinc and the filtrate is concentrated in vacuo. The residue is dissolved in ether and washed with water and saturated sodium bicarbonate solution. The ethereal solution is evaporated to leave a clear yellow gummy residue weighing about 120 g. This residue consists es- 'sentially of the substancerepresentable'byithe The above residue is then subjected to mild alkaline hydrolysis as hereinbeiore described.

Example 2 Pseudo-trillin acetate is obtained and oxidized to its 0-16 ester as described in Serial No. 393,666. It is then subjected to mild alkaline hydrolysis as hereinbefore described, forming a A -20-keto steroid having an unacylated sugar residue attached to the steroid nucleus.

Example 3 Pseudo-sarsasapogenin-u-glucoside penta-acetate is prepared as described in Serial No. 393,666. This substance may be represented by the following structural formula,

by treating said acylated glycosidic derivative with an alkaline reagent withproduction of an unacylated glycosidic derivative of a steroid havingin ringD-the structure. j

and having an unacylatedsugar residue attached a to the steroid nucleus. 1 V

2. The process which comprises mildly oxidiz ing a glycosidic derivative of a pseudo-sapogenin acylated at least at the exo-hydroxyl; group and in the sugar residues, with production of an acylated glycosidic derivative of a steroid having in ring D the structure CHI O CH:

D l u N-O-C-CHr-CHr- H-CHr-O-acyl subjecting said acylated glycosidic derivative to hydrolysis with an alkaline reagent, with production of a glycosidic derivative of a steroid having in ring D the structure CHi H; I

and having an unacylated sugar residue attached to the steroid nucleus.

3. The process for the preparation of steroidal compounds which comprises isomerizing and acylating the side chain attached to ring D or It is subjected to mild alkaline hydrolysis as hereinbefore described forming the corresponding A -20-keto steroid having an unacylated sugar residue attached to the steroid nucleus at C3.

a glycosidic derivative of a steroidal sapogenin by reacting said glycosidic derivative with an acylating agent under conditions more vigorous than those required fo mere acylation, with production of a glyicosidic derivative of a pseudo- 'sapogenin acyla'ted at least at thevexo-hydroxyl group and in vthe "sugar residues; mildly oxidizing said acylated glycosidic pseudo-sapogenin derivative in the side chain attached to ring D, with production of an acylated glycosidic derivative of a. steroid having in ring D the structure and subjecting said acylated glycosidicderivative to hydrolysis with an alkaline reagent, with production of a glycosidic derivative of a steroid having in ring D the structure 4. The process which compriseshydrolyzing an acylated'glyco'sidic derivative 'of a ing in ring D the structure U CH: CHI

by treating said acylated glycosidic derivative with an alkaline reagentofthe class consisting of cold sodium methylate solution, barium hydroxide solution, calcium hydroxide solution and steroid hav-'- 7 cold sodium hydroxide solutiornwith production of an unacy lated glycosidic derivative of a steroid having in ring D the structure and having an unacylated sugar residue attached to the steroid nucleus. t

RUSSELL EARL MARKER. HARRY MEANS CROOKS, JR. EUGENE LEROY WIT'I'LE. 

